Snap-action device



A ril 30, 1963 J. w. WELSH 3,088,012

SNAP-ACTION DEVICE 2 Sheets-Sheet 1 Filed Oct. 20, 1959 I NV EN TOR.

April 30, 1963 J. w. WELSH SNAP-ACTION DEVICE 2 Sheets-Sheet 2 Filed Oct. 20, 19-59 ABCDE 1 INVENTOR.

Jams" /4,/ fl flm BY /W#A1W Armin/Hf! 0 #IIII V G I I I Y FII II Z I I I E I E a E 0 I I v, I M c c I I I I 7 N 0 B I I A I I I 0 bfikbu United States Patent by mesne as- This invention relates to a new and efficient snap-action device and more particularly to a snap-action device which incorporates a new and efficient snap-action vane uniquely mounted in the device.

Electrical snap-action devices which are used to control electrical circuits such as in automobile blinker systems are old and heretofore have used the general combination comprising a flat metal vane incorporating various metallic reinforcing members, ridges or slots across the surface of the vane or affixed thereto. The ribbon is provided with means so that it may be heated and expanded to permit movement of forces within the vane causing the same to snap. When the ribbon is cooled, the ribbon will contract, reversing the movement of forces within the vane.

'Ihe vane must be constructed to withstand the movement of these forces created by the expansion and contraction of the ribbon or by other known means and provide repetitive snap-action caused by said movement.

Heretofore there have been many kinds of vanes mounted in a number of ways which have been used for this purpose. However, each one of these vanes has disadvantages which are overcome by the vane and mounting of the present invention.

The majority of the vanes in present commercial use incorporate embossed ridges running either diagonally across the vane or horizontal or perpendicular thereto. These embossed ridges are incorporated to compensate and guide various forces that are set up in the vane when it is moved by the expansion or contraction of the ribbon or other means and direct the vanes movement in such a manner that it will produce the necessary snapping action. These embossments are incorporated in the vane by a machine bending or press-stamping procedure, which operation inherently causes new and unpredictable forces to be created in the vane which frequently are detrimental to the desired operation of the vane and weaken the entire structure.

It is also common to find that the vane material used today requires an annealing operation during its manufacture which changes the normal static forces that exist in the vane material. Because of the various mechanical and heat treatments of vanes, it is difficult to predict with any degree of accuracy the reliability and the exact action that may be obtained from any particular vane.

The present invention overcomes these disdvantages by eliminating mechanical bending or hammering and by not requiring heat treatment prior to formation of the vane. As a result, the known internal bending forces of the vane are always arranged to react in a reliable known manner when the vane is stressed and snapped by the expansion and contraction of an attached metallic ribbon. The particular arrangement of this invention allows a comparatively small force to balance a large force, namely, the ribbon force balancing the vane force.

It is well known that if forces are applied to the surface of a thin resilient piece of strip metal, bending will occur. The greater the force so applied, the greater the bending. The amount that any particular piece of metal will bend depends upon the stiffness factor of the metal and the thickness of the particular piece.

The metal of the snap-action vane used with the present invention is rolled from a piece of heavy gauge metal down to the desired thickness which is preferably be- Patented Apr. 30, 1963 ice tween three and four thousandths of an inch. After rolling, the metal is heated and drawn to the desired hardness, stabilizing all the stresses and strains within the metal, and then roll hardened. The vane material is then passed through shaping rolls or pulled through diamond forming dies to shape a curvature therein without hammering or mechanical bending of the material. The strip of vane material is then cut to the desired length which, for example, would be about one inch. The vane thus used in the present invention is assured of uniformity of stresses and strains within the metal over a complete length or roll.

The convex face of the vane is provided with a high resistance, metallic ribbon which is attached longitudinally to the surface adjacent the edges of the vane by any suitable method such as welds. The longitudinal ribbon is located on the vertical plane approximately midway between the center of the vane and the bottom edge thereof to utilize the difference in coeificient of linear expansion. The side edges of the vane, adjacent the ribbon and the ribbon welds, are angularly bent inwardly from the ribbon to provide increased resistance holding surfaces over the radius of the bend between the ribbon and the vane taking pressure off the connecting points.

Substantially centrally disposed along the longitudinal axis of the ribbon is aflixed an electrical contact. It is preferable to have a contact smaller than the width of the ribbon so that it may be affixed adjacent the bottom edge of the ribbon so that there will be a wiping action between contacts. This contact is aligned with a stationary contact on an electrical terminal. The electrical terminal extends through a base made of Bakelite or the like and is provided with a lug to fit into an electrical outlet.

The opposite or concaved side of the vane, not having the attached ribbon, is affixed to a second electrical terminal midway along its vertical axis and slightly off center along the horizontal axis of the vane. This electrical terminal also acts as a back-stop for the v-ane when it passes through its snapping, thus relieving the load placed on the ribbon. This second electrical contact is centrally disposed in the base and is also provided with a lug to fit into an electrical outlet.

The device embodying the arrangement of parts of this invention provides a snap-action device which is vastly more reliable than those previously known. It has a longer life and will operate under greater temperatures. It is less expensive to manufacture and the vane may be adjusted as to its internal forces after as sembly if the need arises.

lit is, therefore, a primary object of this invention to provide a snap-action device which is provided with a vane that is devoid of stresses and strains caused by mechanical bending or hammering operations or heat treatment which is very reliable in its operation.

Another object of the present invention is to provide a snap-action device having a vane which has a substantially longer operating life and can withstand greater temperatures.

A further object of the present invention is to provide a snap-action device which provides a vane with low stray stresses and strains and which may be readjusted after assembly if the assembly operation weakens the inherent forces.

An additional object of the present invention is to provide a snap-action device which has a wiping action between the contacts.

Still another object of the present invention is to provide a snap-action device which is constructed to retard uneven working or flapping action of the vane.

Another additional object of the present invention is to provide a vane to which a metallic ribbon may be securely attached without overlapping the sides of the vane.

Another object of the present invention is to provide a snap-action device which has a simple construction and is inexpensive to manufacture and which is adapted so that the vanes internal stress can be changed, making replacement unnecessary.

A still further object of the present invention is to provide a vane mounted on an electrical terminal which acts as a back-stop when the vane is under maximum stress, thus relieving the pressure on the ribbon.

Other additional objects and advantages of the present invention will be recognized during a reading of the following description taken in conjunction with the accompanying drawings referred to, wherein:

FIG. 1 is a side perspective view of the snap-action device of this invention showing it in the completed form suitable for installation;

FIG. 2 is a bottom tion device;

FIG. 3 is a top cross-sectional view taken along line 3-3 of FIG. 1 showing the contacts in a closed position;

FIG. 4 is a top cross-sectional view similar to FIG. 3 showing the cointacts in an open position;

FIG. 5 is a side cross-sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a side cross-sectional view taken along line 66 of FIG. 5 showing the contacts in a closed position;

FIG. 7 is a side cross-sectional view similar to FIG. 6 showing the contacts in an open position;

FIG. 8 is a perspective view of the vane in its normal position;

FIG. 9 is a perspective view of in its snapped position;

FIG. 10 is a diagrammatical tion of the vane; and

FIG. 11 is a current-time diagram relating to FIG. 10.

Referring now to the figures wherein the preferred embodiment of the invention is illustrated, the snapaction device is provided with a base member 20 having a shape commensurate with its particular use. Normally, the base member 20 is either circular, as shown in the figures, or rectangular and is made from a rigid insulating material such as Bakelite. The base is provided with a covering member or cap 21 having a peripheral flange 22 adapted to register over the base 20 and is rolled or crimped to secure the cap to the base. The cap is preferably made of a metal, such as aluminum, which may be suitably shaped and rolled or orimped.

Secured within the base member 20 are two electrical terminals 23 and 24 which have lugs 25 and 26 extending through the base and adapted to be inserted into an electrical socket. The socket generally used with devices of this nature have lug receiving apertures that are perpendicular and spaced from each other, therefore, the lugs 25 and 26 that protrude from the base 20 are likewise perpendicular and spaced from each other as shown in FIGS. 1 and 2.

The electrical terminals 23 and 24 are angled, as at 27, within the base as shown in FIG. 5 and have arms extending through the top of the base. The arm 28 of terminal 23 is centrally disposed within the base member 20 and extends perpendicular thereto. The arm 29 of terminal 24 protrudes through the base member 20 and has its flat surface perpendicular to arm 28. The protruding arm 29 is angled so that it crosses in front of and in spaced relationship to arm 28.

The electrical terminals are preferably made from cold rolled steel and provided with a cadmium plating so that they'may conduct electric current and be corrosion resistant.

The snap-action vane 40 of this invent-ion comprises a thin metallic piece of metal curved along its horizontal axis to provide a convexed front face 38 and a concaved perspective view of the snap-acthe vane showing it illustration of the operaback face 39, as shown in FIG. 8. The vane is constructed so that it is adapted to be bent inwardly against the curvature and tend to flatten out when a force is exerted at the side edges 41 and 42. It has been found preferable to construct the vane from a metallic compound susbtantially comprising nickel or nickel-cobalt since this metal can withstand excessively high tempera tures and it can be rolled to a very thin cross-section, for example, three to four thousandths of an inch, and it has an exceedingly long life spring action despite repetitive bending and snapping action to which it is exposed. In addition, it may readily be shaped to the desired curvature without disrupting the normal static forces inherent in the metal. A high nickel or nickel-cobalt alloy metal is not fragile and is readily adaptable to be bent at the corner edges as will hereinafter be described.

In designing the vane of this invention, the arrangement of the various static and kinetic forces must be consistent with each repetitive bending action so that the same results are achieved from each repetitive snapping of the vane. The forces also must be arranged in such a manner that a comparatively small force exerted on certain sections of the vane, as for example at the edges, will counterbalance a much larger force within the vane itself, as for example the curvature.

The vane, as shown in FIG. 8, has a slight radius or curvature running across its horizontal axis or the width to provide a convexed front face 33 and a concaved back face 39. The amount of curvature depends upon the particular size of the vane and more particularly, upon the parameter of the vane. When force is applied along the side edges 41 and 42 at a point spaced between the central horizontal axis and the bottom edge 43, the curvature will tend to straighten out and break at its weakest point which is vertically at the center of the horizontal axis. The forces reacting in this manner on the vane produce a similar reaction that is experienced in a toggle joint. It can be readily seen that as the forces are exerted on the Sides and the vane becomes flattened, greater resistance is created in order to break down the channel or curvature of the vane. The maximum resisting force of the vane is created when the vane completely flattens and then snaps.

When the vane has passed through its flattened position and has snapped, there is created in the center of the vane a depression or saucer-like curvature 45 which extends throughout most of the height of the vane and through a substantial part of its horizontal surface. This saucer-like depression is shown in FIG. 9 and will be explaincd in more detail with FIG. 10.

It is understood that the rectangular vane shown and described may be square or round, provided it has the curved faces.

To provide the necessary forces at the sides 41 and 42 of the vane 40 as previously explained, a very thin metallic ribbon 50 is attached to the vane adjacent its side edges as at 51 and 52 by electrical spot-welding or the like. The ribbon 50 is preferably made of a high resistance metal such as a nickel-chromium alloy which has a different coeificient of expansion than the vane itself. The ribbon '59 is attached to the sides of the vane in an area spaced between the center of the vertical axis of the vane and the bottom edge 43. By attaching the ribbon in this position it has been found that the terminal arm 28 can be used as a back-stop, preventing excessive stresses from being exerted on the ribbon.

The bottom corners 53 and 54 of the vane 49 are bent or angled inwardly so that part of the ribbon adjacent the edges 41 and 4-2 is bent inwardly. It has been found that by bending the vane in this manner after the ribbon has been attached, it assists in holding the ribbon because of the increased friction caused by the radius at the bend angle, and tightens the ribbon to provide maximum static pulling force at ambient temperature. It should be noted that the material of the vane permits this bending without changing the vanes stresses and strains and since the material is not brittle, it will not break off at the bend. The bending of the attached ribbon on the hypotenuse of the corner triangle, in addition to giving greater frictional cross-sectional area, also relieves the forces on the attaching weld.

The ribbon 50 is provided with an electrical contact 55 which has a height less than the height of the ribbon. The electrical contact 55 is positioned on the lower section of the ribbon in a horizontally disposed area that is slightly off the center line. It has been found that off-centering the contact 55 about one thirty-second of an inch assists in producing uniformity and reliability of the operation of the vane, while the positioning of the contact on the bottom part of the vane provides a wiping action between the contacts. By mounting the vane slightly off-center on the terminal arm 28, one side of the vane is always moved first since it is exposed to change in temperatures of the ribbon first. This avoids any possibility of a reverse snap of the vane due to one side snapping first and then the other side snapping.

The angled arm section 29 of electrical terminal 24 is provided with a second contact 56 which is aligned with but horizontally spaced from the contact 55 of ribbon S0.

The concaved back face 39 of vane 40 is attached to the perpendicular arm 28 of terminal 23 by a weld or the like. As previously described, the terminal arm 28 is centrally disposed in base '20. The vane is affixed to this terminal arm at a position slightly off the horizontal center of the vane similar to the mounting of the contact 55 on the ribbon 50. The weld or the like, holds vane 40 to terminal arm 28 and is preferably located in the center of the vertical axis of the vane, thus providing spaces 58 above and below the concaved surface 39 of the vane 40 and the terminal arm 28.

When the vane snaps to its normal static position with the expansion of the ribbon 50, the bottom edge 43 of the vane is pressed against or stopped by the terminal arm 28, thus preventing any excessive pressure on the ribbon Stl. This feature substantially increases the life of the vane and ribbon since undue stresses and strains are avoided and there is far less fatigue within the vane.

The operation of a snap-action device of this invention is shown in FIGS. 3 and 4 and also in FIGS. 6 and 7.

FIGS. 3 and 6 show the snap-action device just after the ribbon 50 has cooled or is at substantially ambient temperature. Since the ribbon is cool, it is at minimum length and possesses a predetermined amount of kinetic energy. This energy is imparted to the vane at the corners 53 and '54, reversing the normal bend of the vane and tending to buckle the center portion in a saucer-like fashion 45 as shown in FIGS. 9 and 10*. The mechanical energy stored up in the vane at this position is at a maximum.

The contact 55 on ribbon Si is in registration with the contact 56 on terminal arm 2% of terminal 24. This cornpletes the circuit, permitting the flow of electricity through the contacts to the ribbon which, like any resistance, becomes heated. The temperature at the contacts is usually between 300 F. to 400 P. which is imparted to the ribbon.

As the ribbon is heated, it expands, diminishing the force it is exerting at the edges of the vane, and permits the kinetic energy within the vane to seek its normal static position where its forces are in equilibrium. As the ribbon expands, the vane approaches its normal curvature withdrawing the ribbon with it and disengaging contacts 55 and 56.

The vane then snaps or flops into its static position where the forces are in equilibrium balance. This is shown in FIGS. 4 and 7. The vane 40 has its normal curvature with the bottom edges pressing against the terminal arm 28.

Since there is no electric current flowing through the ribbon, its temperature decreases causing it to contract.

6 The ribbon exerts pressure on the corners of the vane forcing it into a reverse bend and buckling it at the center. This contraction continues until the contacts 55 and 56 meet and the ribbon is then heated as described above. The operation described above is then repeated.

The contact 55 is affixed to the bottom edge of the ribbon rather than in a centrally disposed position to cause the ribbon to turn or bend slightly about its horizontal axis with the initial mating of the contacts 55 and 56. This causes a wiping action between said contacts which assures long life and smooth breaking of said contacts.

FIG. 10 diagrammatically illustrates the theoretical relationship between the vane and the ribbon as effected by the thermal expansion and contraction of the ribbon. FIG. 11 illustrates the current-time diagram relating to FIG. 10.

FIG. 10(A) illustrates the relationship between the vane and the ribbon when the ribbon is at ambient temperature. FIG. 10*(E) illustrates the relationship between the vane and the ribbon when the ribbon is expanded to its maximum length through the application of heat. The intermediate sub-figures of FIG. 10 illustrate the theoretical movement of the vane in relationship to the ribbon between these two extreme positions.

In FIG. 10 (A) the ribbon is at its minimum length because of the ambient temperature and possesses a predetermined amount of kinetic energy. This energy is imparted to the vane by causing a contracted reverse bend of the vane. The vane, in this reverse bend position, generates potential mechanical energy which is restrained by the ribbon. The kinetic energy of the ribbon is imparted to the vane by bending the corners of the vane inwardly after the ribbon has been affixed to the outside of the vane. It can readily be seen that in this bending operation the wire, being on the outside, travels a greater distance around the radius of the bend than the corners of the vane which have a smaller radius.

When the ribbon is cooled and at its minimum length, it retains the maximum forces within the vane so that they give the vane a reverse bend and buckle the center portion in a saucer-like fashion as shown diagrammatically in FIG. lO(A).

FIG. 10KB) shows an increase in the temperature of the ribbon and consequently an elongation. As the ribbon expands it permits the kinetic forces in the vane to diminish and tend to approach their normal static equilibrium. It can be seen in FIG. 10(B) that as the ribbon expands, the depth of the substantially centrally disposed saucer-like buckle increases in diameter and tends to flatten the overall parameter.

In FIG. 10(C) the ribbon has expanded even farther due to increased temperature caused by the continued heating of the ribbon. As previously described, when the ribbon continues to expand and permit the kinetic energy within the vane to approach its normal static position, the forces in the vane approach equilibrium. In FIG. 10(C) the saucer-like depression is increased in radius and the parameter of the vane is approaching a flattened position.

As the saucer-like depression is flattened and expands, the fulcrum of the forces within the vane, which are re leased by the expansion of the ribbon, moves away from the central axis toward the outer edges as the ribbon expands.

FIG. 10(D) illustrates the relationship between the vane and the ribbon when the ribbon has almost attained its maximum pre-set temperature and consequently expansion and the forces within the vane are verging upon their static equilibrium balance. A small increase in the temperature (see FIG. 11) of the ribbon shown in FIG. 10(D), will increase its length very slightly but of sufficient amount to disrupt the forces of equilibrium in the vane so that it will flop or snap into its static position which is juxtaposed the ribbon as shown in FIG. 10(E). When the forces in the vane pass through equilibrium, they tend to act in an opposite manner to exert pressure which reacts upon the inherent spring forces in the vane to snap it into its static position.

FIGS. (F), (G) and (H) show the relationship between the vane and the ribbon as the temperature of the ribbon decreases and thus shortens the length of the ribbon. When the ribbon shortens, it imparts into the vane kinetic energy opposing the static biasing effect of the channel. The ribbon kinetic energy first tends to straightenthe vane and then upon further decrease in length the ribbon, the kinetic energy in the ribbon causes the vane to buckle the center section into a saucer-like shape as shown in FIG. 10=(A).

The vane of this invention is constructed so that the discussed saucer-like depression will not be shaped throughout the horizontal length of the vane because of the curvature of the vane. The normal curvature of the vane flattens out and acts as a biasing force. The outside forces of the curved or channeled vane counterbalance each other and prevent the saucer-like depression from forming a channel or V-shaped groove.

If a contact is affixed to the ribbon in a substantially centrally disposed position and aligned with a second stationary contact, the forces, as described in FIG. 10(A), will be supplemented by an additional force caused by the mating of the contacts as the vane approaches its state of equilibrium and snaps or flops into its static position.

When the forces in the vane, as shown in FIG. 10(A), approach equilibrium and go into the snap position, they tend to diminish. However, this diminution of force is supplemented by a counteracting force between the ribbon contact 55 and a fixed contact 56 so that the combination of all forces exerted by the vane and the mating of the contacts is substantially the same at all times.

Although only the preferred embodiment of the snapaction device of this invention has been described herein, it is understood that certain changes and additions or uses may be made without departing from the spirit and scope of this invention. Certain changes and additions may be made to the various attachments and structures which would be within the normal skill of those skilled in the art.

Having thus described the preferred embodiment of the present invention, it can be seen that it affords a new and improved snap-action device.

I claim:

1. A snap-action device comprising a curved resilient metallic vane, said vane being longitudinally curved about its transverse axis and having a convex front face and a concaved back face, a base, a pair of electrical terminals, said terminals having arm elements extending from said base in spaced relationship, the concaved back face of said vane affixed one of said arms at a centrally disposed area slightly off the longitudinal axis of said curved back face, an electrical contact affixed the other of said arms, a thin metallic ribbon affixed the convex front face of said vane and provided with an electrical contact, said ribbon contact aligned with said arm contact.

2. A snap-action device comprising a curved resilient metallic vane, said vane being longitudinally curved about its transverse axis and having a convex front face and a concaved back face, a base member having a pair of electrical terminals, said terminals having upwardly extending spaced arms extending from said base, an electrical contact afiixed one of said arms, the concaved back face of said vane centrally afiixed the other of said arms, a thin metallic ribbon longitudinally aflixed the convex front face of said vane between the center and one horizontal edge thereof, said vane provided with a pair of angled corners overlapping said ribbon, said ribbon provided with a contact, said ribbon contact registering with said terminal arm contact.

3. A snap-action device comprising a curved resilient nickel alloy vane, said vane being longitudinally curved about its transverse axis and having a convex front face and a concaved back face, said vane having top and bottom edges and side edges, a thin nickel, chromium, iron alloy ribbon, said ribbon longitudinally affixed the convex front face of said vane between the center and bottom edges thereof, the bottom corners of said vane provided with triangular inwardly bent sections, said bent sections including the end portions of said ribbon, said ribbon provided with an electrical contact, a base member, said base member provided with a pair of electrical terminals, said terminals having spaced arms extending above said terminals, the concaved back face of said vane afiixed one of said terminals at a centrally disposed area slightly off the longitudinal axis of said curved back face, an electrical contact afitxed the other of said terminals, said terminal electrical contact registering against said ribbon contact.

4. A snap-action device comprising a curved resilient nickel alloy vane having a convex front face and a concaved back face, said vane having top and bottom edges and side edges, a thin nickel, chromium, iron alloy ribbon, said ribbon longitudinally afiixed the convex front face of said vane between the center and bottom edges thereof, the bottom corners of said vane provided with triangular inwardly bent sections, said bent sections including the end portions of said ribbon, said ribbon provided with a centrally disposed electrical contact adjacent the bottom horizontal edge thereof, a circular base member provided with a pair of electrical terminals, said terminals having flat arm members extending above said base, one of said arms being centrally disposed in said base, said vane afiixed said arm at a centrally disposed area slightly off the longitudinal axis of said vane, the other of said electrical arms having its fiat surface perpendicular to and angled in front of said centrally disposed electrical terminal arm, sa-id angled arm having an electrical contact registering against said ribbon contact.

5. A snap-action device comprising a base member having electrical terminals, said terminals protruding above said base member, a resilient nickel alloy vane transversely curved about its longitudinal axis to provide a convex front face and a concaved back face, said back face afiixed one of said protruding electrical terminals, at a centrally disposed area slightly off the longitudinal axis of said curved back face, said convex front face provided With triangular backwardly extending bottom corners, a thin metallic ribbon aflixed the top of said triangular backwa-rdly extending corners and extending longitudinally across said convex front face in taut condition whereby said vane is buckled inwardly at the central vertical axis and flatly adjacent its sides, said ribbon provided with a centrally disposed contact adjacent one longitudinal edge thereof. an electrical contact affixed the other of said protruding electrical terminals, said terminal contact aligned against said ribbon contact.

6. A snap-action device comprising a curved resilient metallic vane longitudinally curved about its transverse axis and having a convex front face and concaved back face, a base, a pair of electrical terminals, said terminals having arm elements extending from said base in spaced relationship, the concaved back face of said vane affixed one of said arms at a centrally disposed area slightly oii the longitudinal axis of said curved back face, an elec trical contact afiixed the other of said arms, said convex front face provided with triangular backwardly extending bottom corners, a thin metallic ribbon aifixed the top of said triangular backwardly extending corners and extending longitudinally across said convex front face in taut condition whereby said vane is buckled inwardly at the central vertical axis and flatly adjacent its sides, said ribbon provided with an electrical contact, said ribbon contact aligned with said arm electrical contact.

7. A snap-action device comprising a dielectric base having a pair of electrical terminals, each of said terminals provided with an arm extending through said base, a resilient metallic vane curved about its longitudinal axis to provide a convex front face and a concaved back face, a high electrical resistant thin metallic ribbon, said ribbon longitudinally aflixed across the convex front face of said vane and affixed adjacent the side edges thereof in an area between the vertical center of the vane and the bottom edge thereof, said ribbon afiixed said vane under tension whereby said vane is flattened at its sides and centrally buckled along the vertical axis, said vane adapted to expand with an increase in temperature thereby releasing said vane to return to its normal fiat surface curved about its longitudinal axis, said ribbon provided with centrally disposed electrical contact adjacent its longitudinal edge, the back concaved face of said vane afiixed one of said terminal arms in a central area along its vertical axis and slightly off the central area of the longitudinal axis, the bottom edge of said curved vane pressing against said terminal, said terminal provided with an electrical contact, said arm contact aligned against said ribbon contact when said vane is in its buckled position, and aligned with and spaced from said contact when said vane is in its normal positon.

References Cited in the file of this patent UNITED STATES PATENTS 2,041,775 Mottlau May 26, 1936 2,615,106 Schmidinger Oct. 21, 1952 2,706,227 Welsh Apr. 12, 1955 2,842,642 Colombo et al July 28, 1958 2,861,149 Hollis et al Nov. 18, 1958 2,878,340 Uhl Mar. 17, 1959 

1. A SNAP-ACTION DEVICE COMPRISING A CURVED RESILIENT METALLIC VANE, SAID VANE BEING LONGITUDINALLY CURVED ABOUT ITS TRANSVERSE AXIS AND HAVING A CONVEX FRONT FACE AND A CONCAVED BACK FACE, A BASE, A PAIR OF ELECTRICAL TERMINALS, SAID TERMINALS HAVING ARM ELEMENTS EXTENDING FROM SAID BASE IN SPACED RELATIONSHIP, THE CONCAVED BACK FACE OF SAID VANE AFFIXED ONE OF SAID ARMS AT A CENTRALLY DISPOSED AREA SLIGHTLY OFF THE LONGITUDINAL AXIS OF SAID CURVED BACK FACE, AN ELECTRICAL CONTACT AFFIXED THE OTHER OF SAID ARMS, A THIN METALLIC RIBBON AFFIXED THE CONVEX FRONT FACE OF SAID VANE AND PROVIDED WITH AN ELECTRICAL CONTACT, SAID RIBBON CONTACT ALIGNED WITH SAID ARM CONTACT. 